different matter.

The Indian, therefore, must have thought the tinder-box a wonderful invention.

In these cases fire is produced by the oxygen of the air uniting with the wood of the Indian, with the steel of the tinder apparatus, and with the phosphorus of the lucifer match. It is heat in each case that causes the union. The match takes fire easiest, because little heat is required to make phosphorus unite with oxygen. You can produce enough heat for this by slight rubbing. It is supposed by some, that many of our fires are occasioned by phosphorus or lucifer matches carelessly left about. A cat or a mouse might knock them off a shelf; and if they should happen to fall upon something combustible, as paper, or clothing, a fire might result.

What you see on the end of a match is not phosphorus alone, but a mixture of this with some other substances, which make it burn more readily than if it were alone. The reason being that they have oxygen in them; and the more oxygen there is to unite with the phosphorus, the more readily will it burn. In lighting the match, friction makes the phosphorus unite with the oxygen in the mixture, in addition to that in the air.

Machinery is sometimes set on fire from heat occasioned by friction; that is, the iron becomes so hot that it heats the wood sufficiently to make the oxygen of the air unite with it. If the axles of railway carriages are not kept well greased, heat produced by the friction sets the little grease that is in the axle-boxes on fire; that is, makes the oxygen of the air unite with it.

The knife-grinder with his rapidly revolving wheel, or disk of stone, makes the sparks fly off, really burning part of the knife that he is grinding.

"Easy Introduction to Chemistry."

Edited by the REV. A. RIGG.

1. FLINT, a very hard kind of stone, formed chiefly of an element called silica. Flints are found chiefly as pebbles, more or less rounded, among the chalk of the South Downs, &c. Flints were formerly used as arrow-heads, and the word comes from the A.-S., and means literally arrow-stone..

ANIMAL HEAT.

WHAT makes your body warm? You will perhaps say clothes and fires. No; they help to keep you warm, but they do not make you so. The heat that makes you warm is produced in your own body, and is made by real combustion. There is, as it were, a fire in your body. It is a real fire, though there is neither flame nor light.

This is one reason why you cannot live without oxygen. This gas is needed to keep up the fire in your body, just as it is needed to keep all fires burning.

In the results of the combustion, the burning in your body is like the burning of a common candle. The oxygen of the air unites with the carbon of a candle to form carbonic acid, and with the hydrogen of a candle to form water. So, also, the oxygen that enters your lungs unites with the carbon of your body to form carbonic acid, and with the hydrogen to form water. But where in the body does the oxygen find the carbon and the hydrogen? It finds them everywhere. They make, in part, your body as they do the candle. Blood circulates everywhere, to the very ends of your fingers, and so carries the oxygen taken from the air to the lungs. The warmth in your fingers, and in every part of your body, is made by the combination of oxygen with hydrogen and carbon..

But you will ask, "Are carbonic acid gas and water formed in the very ends of my fingers as they are in the

burning candle?" Exactly so. "What becomes of them?" you will say. "Do they go from my fingers into the air as they do from the candle?" Perhaps some of the water does. "But the carbonic acid gas, what becomes of that?" It goes in the blood to your lungs, and there is breathed out into the air.

Part of the food we eat acts as fuel; that is, it supplies the carbon and hydrogen that are continually burned in our bodies. There are some foods that furnish much carbon and hydrogen, and so keep up the fire in us. Sugar is one of these, fat is another. Inhabitants of very cold climates, as the Esquimaux,1 eat large quantities of fat and oil, because they are of use in keeping them warm. They need food that has charcoal in it for fuel, to guard them against the extreme cold of the climate. They love food of this kind. A captain of a vessel invited one of these people to dine with him. His guest declined the coffee and wine which were offered, but, seeing an oil-can near, he took it and drank all the oil. That he liked for he had been accustomed to drink it to keep himself warm. But coffee and wine he did not think of

much use.

Sugar is one kind of food that furnishes fuel for the fire in us. You can hardly believe what a large portion of sugar is charcoal, but so it is. Indeed, sugar and wood are composed of the same things; and as charcoal can be got from wood, so also it can be got from sugar.

You have learnt that the carbonic acid gas, which a man breathes from his lungs in a year, contains about 200 pounds of charcoal. Now this carbonic gas comes from the fire in his body, and in this fire 200 pounds of charcoal unite in his body with oxygen. Where does all the charcoal come from? It is swallowed in the food -in the sugar and fat, &c., that are eaten. You thus

swallow every year an amount of charcoal, which weighs more than you do, and in burning it keeps you warm.

In running and playing you become heated. Think why this is so. The heart beats quicker than when you are still, and therefore blood flows very rapidly in the arteries and veins. At the same time you breathe quickly. Now the quick breathing introduces more air, and therefore more oxygen, into the lungs; more oxygen of course enters the blood, and as the circulation is quickened the oxygen is carried everywhere more quickly. The internal fire must therefore burn more briskly in every part of the body, for the same reason that fire in a fireplace burns more quickly by blowing. Oxygen in both cases, in the fire in the body as well as in that in the fireplace, comes faster to the carbon and hydrogen.

Did you ever think that your body is always giving out heat to the air? Even in very hot weather the air is almost always cooler than the body. You are uncomfortably warm on a hot day, because your body does not give off enough heat.

A large number of persons, therefore, when crowded together give out much heat. We see this illustrated in large parties. When only a few persons are present, the rooms are comfortable; but when many are assembled, the air becomes uncomfortably warm. If a hundred persons are present, we may think of them as a hundred fires warming the air.

Again, if you stand still without sufficient clothing you become chilled. Observe how this is; the air is passing into your lungs carrying in oxygen, which keeps the fire in you burning, but the fire is not sufficient to keep you warm, because the air is so cold, that it receives much heat from the outside of your body.

How may this be remedied? In two ways.

One is to make the fire in your body burn more briskly; this can be done by exercise, such as running, jumping, working, &c. Then the blood circulates quicker, and you breathe faster; so more oxygen enters, and brightens up the fire, in the same way as the fire in a grate is brightened by air entering in from a pair of bellows. You have seen persons in cold weather strike their arms across the body and rub their hands together. This is to make the blood flow more freely to the very tips of the fingers, that an abundance of oxygen may be there to unite with the carbon and hydrogen, and so produce sufficient warmth.

Another remedy is to put on more clothing. Thus the heat which the fire in you is constantly making is retained. This is the reason why more clothing is needed, when you are driving in a carriage than when you are walking or playing.

For animals that live in cold countries the Creator provides clothing fitted to retain the heat which is made. in their bodies; they are clothed with furs. Contrast the polar bear and the elephant in this respect. The bear has a good furry coat, while the elephant, that lives in a warm climate, has only a few straggling hairs upon his skin. "Easy Introduction to Chemistry." Edited by the REV. A. RIGG.

1. ESQUIMAUX, a people inhabiting Labrador and the northern shores of America and Asia, where the cold is so intense that vegetable life can scarcely exist. The Esquimaux live chiefly on the flesh and fat of seals, whales, &c. They inhabit huts made of snow, lined with skins, and quite air-tight, so that the heat caused by the combustion of oxygen in their bodies may not, escape.

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